Utilizing a variety of analytical methods (statistical numerical, and sequence homology studies) an evaluation of the variation in retroviral proteins produced by both murine and human (HIV) viruses has been performed. These studies have attempted to define conserved and variable regions of both the murine and human viral genes. In this way portions of retroviral genes that might be essential for viral replication (i.e. conserved) have been identified. These regions are candidate areas for mutagenesis studies directed toward the understanding of and the intervention in viral replication. Microcomputer software has been developed to allow a rapid and accurate analysis of gene mapping studies. When applied to data obtained in studies utilizing DNA from mouse-CHO hybrid cell lines successful results were obtained.